Prof. D. N. Singh

IYER KANNAN RAMAN

Ph. D.
Indian Institute of Technology Bombay, Powai, India kannankr20@rediffmail.com

INVESTIGATIONS TO ESTABLISH INFLUENCE OF VRIOUS PARAMETERS ON SUCTION CHARACTERISTICS OF FINE-GRAINED SOILS

The soil mass exists in different states (viz., undisturbed, reconstituted and compacted) and under prolonged influence of mechanical and thermal energy fields might attain unsaturated state. This state of the soil mass is essentially due to the variation in its moisture content, which in turn controls its suction, and would mainly affect the stability and performance of various geotechnical structures located over it and made with it. The relationship between these parameters is quantified by the soil water characteristic curve, SWCC. In the recent past, it has been demonstrated by the researchers that the SWCC is not 'unique' and it depends upon several soil specific parameters (viz., clay content, silt content, specific surface area, cation-exchange capacity, state of compaction and linear shrinkage) and the drying- and wetting- paths adopted. Based on these studies, though, various models have been proposed to predict the drying- and wetting- path SWCCs of the soil mass, the role of various soil specific parameters on these SWCCs, and the hysteresis associated with them, has not been studied in details. This calls for an extensive study, which would include the microstructural changes undergone by the soil mass during its drying and wetting. With this in view, drying- and wetting- path SWCCs were developed for the soils of entirely different characteristics and the hysteresis between these paths, defined as ?suction hysteresis?, was correlated with the soil specific properties and the pore-size distribution characteristics obtained by employing the mercury intrusion porosimetry. The study brings out clearly the influence of the state of the soil mass on its SWCC. Furthermore, a ?deformable capillary tube? hypothesis, which would be quite useful for defining the suction characteristics of swelling clays has also been proposed.